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KING COUNTY, �' �+ SHINGTON, SURFACE V✓ ATEk DESIGN MANUAL <br /> TABL CS WESTERN WASHIItiGTON RUNOFF CURVE NUMBERS � <br /> SCS WESTERN LYASHINGTON RUNOFF CURVE NUMBEHS (PuW�shed by SCS in 1982) <br /> RunoH curve numbers for selected agr�cultura�, suburban and urban land use tor Type �A <br /> raln(ail distribution, 24•hour storm duratbn. CURVE NUMBERS BY � <br /> HYDRO LO B�C SOICL GR pUP <br /> IAND USE DESCRIPTION � 9t gq 95 <br /> winter condRion 74 82 B9 92 <br /> CultNated�and(1): rasslands <br /> n areas: low 9rowing brush and 9 �8 � 89 <br /> Mountain ope 65 <br /> Meadrn'i or pasture: 42 gq 76 et <br /> undisturbed or older second growlh 55 �p 0� 86 <br /> yyood orforestiand: ,econd growth orbrush 81 gg 92 � <br /> ydood ortorestland: young : � <br /> Orchard: with covercrop <br /> ppen spaces,�awns, parks, 9olf courses, cemeteries, <br /> landscapi�9• grass cover on 75% 5g 80 � � <br /> good condftlo�. or rnore of the area <br /> grass cover on 50% �7 85 � 92 <br /> fair condriion: to 75% ol the area <br /> 76 85 d9 91 .` <br /> rkin lots 72 82 87 89 � , <br /> Gravel roads and pa 9 <br /> Dirt roads and parki�g lots 98 98 98 98 <br /> �mpervious surlaces, pavement, roofs, etc• <br /> nds, etc. 100 100 100 100 <br /> ppen water bodles: lakes,wetlands,po <br /> Single Family Residential (2) <br /> %Impervious (3) Se�rote curve number <br /> pweiling Unk/Gross Acre 15 shall be selected <br /> 1.0 DU/GA 20 Ior pervious and <br /> 1.5 DU/GA 25 �mpervfous portlon <br /> 2.0 DU/GA 30 of the site or basin <br /> 2.5 DU/GA 34 <br /> 3.0 DU/GA 38 <br /> 3.5 DU/GA 42 <br /> 4.0 DU/GA 46 <br /> 4.5 DU/GA 48 <br /> 5.0 DU/GA 50 <br /> 5.5 DU/GA 52 <br /> 6.0 DU/GA 54 <br /> 6.5 DU/GA 56 <br /> 7.0 DU/GA <br /> %impervious <br /> Planned unit developments, mus[be comp�Red <br /> condominiums,apartments, <br /> commercial business and ineering <br /> industr�al areas. <br /> ��) For a more detailed descrip�o°�Chapt Ir 8aA�9 st 1�72rve numbers reter to Nationai ng <br /> Handbook, Sectlon 4, Hyd 9Y• �a�i�ion tor these curve numbers. <br /> (p) Assumas roof end driveway runofl is directed into street/storm sys em. . <br /> (3) The remaining peN�ous areas Qawn) are considered to be in 90� <br /> 11192 <br /> 3.5.2-3 • <br /> � <br /> � <br />